M135 Problem, continued with COMPRESSION AND VACUUM TEST info.

[Brad]

I am starting new thread because the other is just too long and involved. Basically as a review, the truck idles well but has no power on the road. So this evening we did vacuum test. Manual says it should be 17 to 20". After some adjusting of the carb idle jets and a little turning of the distributor we are at 19"
As for compression: #1=70# / #2=75# / #3=65 # / #4=70# / #5=75# / #6=70#
These could vary a very little as the gauge I had was the hand held type. But I checked them all twice, but these all seem pretty good. However with this type gauge I think I might have a little more compression than it's telling me?
So if these are correct, seems my vacuum is well with-in spec and the compression is very good with-in spec?
So I wonder what the heck is wrong with this truck??

 

[87cr250r]

My dad gets this on his boat. He doesn't take it out very often but starts it and idles it regularly. The idle circuits stay clean and work fine but once the review to give it some gas the secondaries don't flow fuel because the jets are clogged.

No smoke and no power means you've got no fuel. It may not be as noticeable on a gas engine vs a diesel but it's there.

 

[Brad]

I also discovered last evening that the valve on the crankcase ventilation system actually has no internals. Meaning it is open all the time? Even though it is a very small hole, isn't that a vacuum leak?
Thing is, for 20 years or so since we been running the truck just fine, it has always been like that. So I don't think that could be the trouble. But to be sure I have put temporary plug in the intake manifold where that line attaches for a test run.
This afternoon I plan to go over the entire fuel system again? I am going to look for a clog of course, but am going to make a SSsteel screen for over the line in the tank. As we have it, there is not a filter before the fuel pump, but after. Should this be reversed?
Thing is, there seems to be enormous fuel flow to the carb?

 

[87cr250r]

When I say clog I'm talking jets in the carburetor.

 

[Brad]

I think I understand what you're saying. It's jsu that I am reluctant to take the carb apart as I really do not understand how a carb works, and other than crud and dirt, or something obvious, I would not really know what to look for?
Thanks

 

[GopherHill]

I think you need experienced assistance.

 

[Brad]

I think you are correct. I been begging for it, but no luck locally. So we took a test run this evening and it ran great for 3 or 4 miles. Then it started to lose power. Not a lot, but certainly noticable. We did have an experienced mechanic suggest we change the coil. So when we got back to shop we did. It was pretty warm to the touch?
But it was too late for another run.
So I think I am going to change the oil. Has a definit gasoline odor and seems thin? It has been a few years. We been adding Rotella T4, 15 W 40. Think this is a good choice? We had been advised to use that because it has zinc in it.

 

[87cr250r]

You need to look at the API rating on the oil. I run Chevron Delo 400 SDE in my fleet. It's an API SN. The zinc content is half of what it was when it was an SL. The newer Chevron formulations are replacing zinc with Boron and Calcium. I think you'll find the same is true for other oil blenders including Mobil.

The last API rating that I would consider fully zinc'd is the SJ rating. That's been obsolete for decades. The only place I have seen the SJ rating is Honda's motorcycle, marine, and lawn mower oils. The GN4 motorcycle oil is a SJ formulation I believe.